Device utilizing electro-viscous liquid



p 29, 1964 s. E. NUBER 3,150,678

DEVICE UTILIZING ELECTRO-VISCOUS LIQUID Filed July 11, 1960 sSheets-Sheet 1 Sept. 29, 1964 s. E. NUBER DEVICE UTILIZINGELECTRO-VISCOUS LIQUID 3 Sheets-Sheet 2 Filed July 11., 1960 Sept. 29,1964 s. E. NUBER 3,150,678

DEVICE UTILIZING ELECTRO-VISCOUS LIQUID Filed July 11, 1960 I5Sheets-Sheet 5 Wm 's dfredo 6. YLubef' Arrows.

United States Patent 3 150,678 DEVICE UTILIZING ELECTRO-VISCOUS LIQUIDSigifredo E. Nuher, South Beloit, Ill., assignor, by mesne assignments,to Warner Electric Brake & Clutch Company, South Beloit, Ill., acorporation of Delaware Filed July 11, 1960, Ser. No. 41,834 14 Claims.(Cl. 317-262) This invention relates to electrostatic devices such asbrakes, clutches, chucks, fluid transfer systems, and the like utilizingthe so-called Winslow effect, that is to say, the stiffening or increasein the shear resistance of a thin layer or film of viscous liquid whensubjected to an electric field. In such devices, the liquid layer isconfined between surfaces across which an electric potential isimpressed to stilfen the liquid and bond the same to the confiningsurfaces thereby controlling the flow of the liquid or its force ortorque transmitting ability.

The primary object is to increase shear resistance of the liquid layerin devices of the above character by providing a more effective electricfield for activating the layer.

Another object is to increase the intensity or potential gradient of theelectric field capable of being sustained by the liquid layer withoutdanger of heating or breakdown while insuring absolute safety in serviceuse of the electro-responsive device.

A further object is to utilize alternating current potential in a novelmanner to produce an electric field of increased efiectiveness.

A further object is to provide an electro-rcsponsive device whichoperates efliciently and safely under high voltage even when exposed toliquids such as conductive coolants or after the accumulation of dirt orother contaminants in the electro-viscous film.

Still another object is to provide a device of the above character inwhich the holding force may be exerted on a non-conductive surface.

The invention also resides in the novel manner of confining theelectro-viscous liquid and imposing the electric field thereon to permitthe use of a wider variety of liquid compositions and either a thickeror thinner layer of liquid than has been possible heretofore.

Other objects and advantages of the invention will become apparent fromthe following detailed description taken in connection with theaccompanying drawings, in which FIGURE 1 is a fragmentary plan view ofan electric chuck embodying the novel features of the present inventionincluding a circuit diagram.

FIG. 2 is an enlarged section taken along the line 2-2 of FIG. 1.

FIG. 3 is a view similar to FIG. 2 showing a modification.

FIG. 4 is a section taken along the line 4-4 of FIG. 1.

FIG. 5 is a diagrammatic view illustrating the path of the electricfield. I

FIG. 6 is a longitudinal sectional view of an electric brake embodyingthe present invention.

FIG. 7 is a fragmentary section taken along the line 77 of FIG. 6.

FIG. 8 is a perspective view of parts of the brake.

3,150,678 Patented Sept. 29, 1964 FIG. 9 is a diagrammatic view of afluid transfer system including a valve embodying the present invention.

FIG. 10 is a fragmentary section taken along the line 1010 of FIG. 9.

7 FIGS. 11 and 12 are sections taken respectively along the lines 11-11and 12--12 of FIG. 10.

FIG. 13 is a diagrammatic view of the wave form of the exciting current.

In prior devices utilizing the Winslow effect, the film ofelectro-viscous liquid has been semiconductive and the exciting electricpotential has been applied directly to opposite surfaces of the film,the stiffening of the liquid thus being accomplished by an actual flowof current through the film. With this method, only thin films usuallyabout .001 to .020 of an inch can be used, and the voltage must belimited to a value that will not cause break-down or objectionableheating of the liquid. These inherent characteristics have limited thecommercial use of such devices.

I have discovered that the actual conduction of current through anelectro-viscous liquid need not be relied on to effect the stiflening ofthe liquid and that the liquid may be made to respond to the so-calleddisplacement currents such as those produced in the dielectric of anelectric condenser when energized by an alternating current voltage.Accordingly, the present invention contemplates interposing a layer ofsolid dielectric material between at least one electrode and theelectro-viscous film so that the resulting sandwich of liquid and solidlayers. forms a composite electric condenser capable of withstandingextremely high voltages.

The invention thus generally characterized may be utilized in manydifferent devices and fluid systems, such for example as a chuck shownin FIGS. 1 to- 4 of the drawings for holding a workpiece duringmachining or other operation thereon, a brake FIGS. 5 to 7 for exertinga retarding torque, and a valve FIGS. 8 to 10 for controlling the flowof liquid in a fluid transfer system. It is to be understood that I donot intend to limit the invention by such illustrative disclosures, butaim to cover all alternative constructions, modifications and usesfalling within the spirit and scope of the invention as expressed in theappended claims.

Many different liquids are electro-viscous and will stiffen appreciablyand bond effectually to the confining surfaces when an electricpotential is impressed across opposite sides of a layer of the liquid soas to create an electric field within the layer. Among the liquidscapable of being used to practice the present invention are Examples Cand D disclosed in Patent No. 2,661,825 and most of the examplesdisclosed in a pending application of Willis M. Winslow, Serial No.19,465, filed April 4, 1960, issued July 31, 1962, as US. Patent No.3,047,507. Each of the latter examples comprises a mixture of fourclasses of ingredients namely: (1) an electrically stable, lowdielectric constant, oleaginous vehicle of suitable viscosity; (2)finely divided and non-conductive solids having an average diameter offrom about 0.1 to about 5 microns and possessing the ability to absorb asignificant quantity of a substance such as water or alcohol; (3) anorganic surface active dispersing agent; and (4) water or a mixture ofwater and a water miscible alcohol or other hydroxy compound.

Typical of the suitable liquids given in said application is thefollowing:

Percent by wt.

.A mixture in proportions of about 2: 1 of 4,4-bishydroxymethyl-2-heptadecencyl-2-oxazoline and oleylamidotriethanolmethane-product of Commercial Solvents Co.

Viscosity of 40-50 Saybolt sec. at 100 F.

Specially ground dehydration grade-about 1 micron average diameter.Davidson Chemical Co. SMR-55 6826.

Primarily ,(about 90%) 1 hydroxycthylQ-heptadecenyl imidazoline. Theremaining 10% comprises oleic acid amide and N-aminoethyl ethanol-amine.Product sold. by Union Carbide.

A silicate ester base coolant-dielectric fluid sold by Monsanto ChemicalCo.

With the present invention, it is possible to employ electr c-viscousmixtures which do not include water as an ingredient. The-following isan example of such a liquid:

Percent by wt. Neutral motor oil (viscosity 90) 30.5 Glycerol monooleate 5.5 Amine220 10.0 Ethylene glycol 4.0 Silica gel, one micron size50.0

It has also been found that certain single component liquids can be usedto form the electro-viscous .film in devices embodying the presentinvention. An example of such a liquid is 1,1'-bis(X-chlorophenyl)ethanemanufactured by Dow Chemical Company and comprising X- chlorophenylethane.

.In the chuck as shown in FIGS. 1 to 5, a workpiece having agenerallyfiat bottom surface 11 of conductive material is supported. ona rigid surface 12 of a suitable base-or'composite block 13'through themedium of a layer or relativelythin film 14 of a suitableelectro-viscous liquid of the character abovedescribed. The block may beclamped onto a work table or other support 9 as by bolts engagingprojecting cars 15. If the workpiece is composed of non-conductive.material such as ceramic, plastic, .glass, wood, etc. having arelatively low dielectric constant, the surface 11 isflashed with metalor otherwise coated with a conductive film suchfor example as ametallicpaint. As'will appear later, workpieces composed ofnon-metallicmaterial of high dielectric constant, that is, more than10,'n1ay be chucked without preliminary coating.

The potential for creating the electric field in'the liquid film 14 isapplied across electrodes 16, .17 and'lS embedded in the base 13 auniform distance, usually about .10of an inch, below the top surface 12.In the present instance, each electrode comprises a thin strip of metalsuch as silver foillying against and preferably bonded to a relativelythin layer 19 of non-conductive or semiconductive material which is setin the base and forms part of the work supporting surface 12. In FIGS. 1and 2, the layer 19 is composed ofseparate bars laterally spaced apartwith the electrode strips covering thebottom surfaces and the top facesflush with each other and defining the surface 12. This relation ismaintained by a rigid body of non-conductive material such as plastic 20preferably cast in and around the electrode bars after attachment ofconductors 21, 22 and 23 thereto and while the bars are held in thedesired relation within an enclosing frame 24. The latter maybe made ofsteel with the ears 15 welded or'otherwise secured thereto. Theplastic'20 is-preferably a so-called potting compound such as an epoxyresin adapted to be cast while cold.

In the form shown in FIG. 3, the layer 19 may comprise a continuousplate with the electrodes 16, 17 and 18 bonded to the bottom thereof inproperly spaced relation as by any well-known technique such as is usedin printed circuitry. As before, the plate is backed solidly by the castbody 20 of rigid plastic. In each instance, the plastic below theelectrodes and the conductors 21-23 is of suflicient thickness toisolate these parts effectually from work table or other metallicsupport to which the chuck may be secured in service use.

The electrodes are sized according to the size of the workpieces to bechucked and the number used is preferably suiiicient to provide .an arealarger than the bottom of the workpiece. For ceratin work shapes, theelectrodes may be of other shapes such for example as concentric rings.

As set forth above, the use of high voltage, for example 2000, forproducing a strong electric field in the liquid film 14 is made possibleby interposing a layer of rigid dielectric material between at least oneside of the film and the electrodes so as to form with the film acomposite "electric condenser. In thepresent instance, the bars 19(FIGS. 1 and-2) or the plate 19 (-FIG. 3) form the dielectric layer.While various dielectric'materials may be employed, optimum voltageacross the film may be achieved -byusing amaterial having a highdielectric constant, that is, more than about 10 (measured at 25 (3.),relative to the dielectric constant-of the electro-viscous'liquid whichlatter is usually about 5 or less.

Among the best such dielectric materials now available is a firedcer-amicsold under the trade name of BT- 15 and described by' themanufacturer, Arnold-Engineering Company of Marengo, Illinois, asproduced from a polycrystalline form of barium titanate with varyingamounts of lead and calcium titanates and cobalt oxide. Asimilar-material known as D-51 and supplied by Central Lab Company ofMilwaukee is composed of barium titanate-with strontium titanate andferric oxide additives.

This material has a dielectricconstant of from 5500 to 6500-and anestimated dielectric strength of 35 to 40 voltsper .001 inch ofthickness.

In addition to its high dielectric constant, the dielectric strength'ofithelayer 19 should be as high as possible in order to impart to theliquid-solid sandwich the desired high res'istanceito breakdown underthe applied voltage even 'though'the layer is relatively thin.Satisfactory results have been achieved with the materials abovedescribed when the layer is .10 of an inch thick.

It will-be observed "that the liquidfilm 14 and the dielectric layer 19'confined as described above between the electrodes and theconductive-bottom surface 11 of the workpiece form in etfect twocapacitors connected in series. .In this relation, the so-called.displacement currents in'the film are, for a given value of appliedalternating voltage, directly proportional to the frequency of suchvoltage and the capacitance of the system. Therefore, it is desirable toselect an electro-viscous liquid having the highest available dielectricconstant and of minimum thickness. The latter, in the case of a workchuck, is determined by the flatness of the bottom surface 11 of theworkpiece in order to insure complete coverage of the work andsupporting surfaces at all points across the opposed areas.

When, 'as in the work chuck above described, all of the electrodes aremounted in one of the members to be coupled by the viscous liquid, theliquid film and the dielectric layer form two sets of capacitors inseries. That is to say, one set is disposed between the conductivebottom surface 11 of the work and an electrode of one polarity, theother set being between this surface and an electrode of oppositepolarity. Thus, the work surface serves not only as one plate of thecondensers of each set, but also as a conductor for connecting the setsof capacitors in series relation.

With this arrangement, the electric field produced by oppositepolarization of adjacent electrodes will be distributed as illustratedin FIG. 5. That is, the displacement currents created by thealternations in the applied voltage will thread the entire areas of theelectrodes and the adjacent alined areas of the dielectric layer 19 andfilm 14, and the latter areas will be bridged by the work surface asillustrated by the lines 26. Shunting of the electric field edgewisebetween the bars while by-passing of the liquid film may be minimized byspacing the bars apart as shown in FIG. 2.

To minimize variation of the force or torque transmitting ability duringalternation of the energizing voltage, the invention, in another of itsaspects, contemplates exciting the film 14 by a polyphase voltage withthe respective components, three in the present instance, applied to thethree electrodes 16, 17 and 18, which are arranged in groups as shown inFIG. 2 with the consecutive numbers of the different electrodes formingeach group and successive groups spaced along the supporting surface 12.As a result, the potential at the respective electrodes will change inaccordance with the usual wave forms a, b and 0 shown in FIG. 13. Thesecurves intersect each other at successive points 27 of positivepotential and similarly at points 28 of negative potential. The

result is that the potential gradient between two electrodes 16 and 17may fall to zero as at one of the points, but between the other pairs ofelectrodes 16, 18 and 17, 18 the gradient will be equal to 30. As aconsequence, the electric field remains effective to excite and stiffenthe liquid of the film 14 at all times in spite of the alternating andchanging value of the voltage of each phase. In this way, the desiredholding force is exerted continuously on the workpiece. The differentcomponents of the polyphase voltage are applied to the three groups ofelectrodes 16, 17 and 18 through insulated conductors 21-23 which areextended into the chuck base through suitable waterproof fittings.

While the desired polyphase current may be obtained from any suitablesource such as a standard alternator, a source more convenient forservice use of the chuck in an ordinary machine shop may be derived froma commercial single phase power line by a converter of the type shown inFIG. 1. The single phase voltage from an auto-transformer 31 isadjustable in magnitude by a slider 32 and is applied to avoltage-increasing or step-up transformer 33 when a switch S is closed.The output is impressed across parallel RC phase shift networksincluding a first resistance 34 and capacitor 35 and a second resistance36 and capacitor 37, the two being reversely connected to produce oneleading phase and a second lagging phase at the output leads 21, 22 and23. This simple type of converter may be used in the present instancebecause the creation of the desired electric field within theelectro-viscous film does not involve an'actual how or conduction ofcurrent through the electro-viscous film 14 but utilizes so-calleddisplacement currents produced by alternating potential as describedabove.

With the components of the chuck constructed and dimensioned as abovedescribed, it is possible to increase the shear resistance of the filmmixture to approximate ly 20 pounds per square inch. In addition, all ofthe electrodes are insulated effectually from each other, from theworkpiece and from the supporting work table.

It will be apparent that the electrodes 16, 17 and 18 are spacedequidistant from the conductive bottom surface 11 of the workpiece andalso that these electrodes are spaced equidistantly from the support 9on which the chuck is mounted in service use. As a consequence, there isformed between the work surface 11 and each pair of electrodes an equalcapacitive coupling. A similarly balanced coupling exists between eachpair of electrodes and supporting metallic structure. These fourcouplings form a symmetrical bridge circuit for each phase of theenergizing potential. Therefore, the machine frame and the workpiece 10are always at the same potential or at zero potential with respect toeach other. This provides absolute safety to the machine operator inspite of the high exciting voltages that may be used.

The dielectric layer 19 associated with the electroviscous film in themanner above described may be used to advantage in torque producingcouplings which may take various forms, a typical one of which is thebrake shown in FIGS. 6 to 8. In this, electrodes 41, 42 and 43 in theform of thin metal disks are molded into disks 44, 45 and 46 of thefired ceramic material above described, each composite disk having apair of radially projecting squared teeth 47 snugly splined intoinwardly opening grooves 48 in a cylindrical shell 49 of rigidinsulating material. The shell is clamped by tie bolts 53 betweenaxially spaced heads 50 also composed of insulating material and boltedto a stationary support 57 supporting bearings 51 in which a shaft 58 isjournaled.

Two additional pairs 51 and 52 of grooves are formed in the shell 49 andangularly spaced from the grooves 48 to receive similar spline teeth 47on the disks 45 and 46. Metallic strips 54, 55 and 56 seated in thebottoms of the grooves 48, 51 and 52 bear against the outer ends ofteeth 44 45 and 46 formed on the metal disks within the lugs 47. Therespective contact strips 54, 55 and 56 are connected to the three lines21, 22 and 23 leading from a three phase alternating current source ofthe type above described.

Interposed between the adjacent disks 44, 45 and 46 are metal disks 60,61 and 62 spline coupled to the shaft 58 and spaced accurately along thelatter by rings 63 separating the adjacent disks from each other, theterminal disks lying adjacent the casing heads 50 in this instance.Narrow axial clearances 65, usually about .010 of an inch, left betweenthe rotating and fixed disks are filled with electro-viscous liquid ofthe character above described.

With this arrangement, the layer of high dielectric material on eachside of the stationary disks 44-46 cooperates with the adjacent liquidfilm 65 to form a composite capacitor disposed between the adjacentconducting disk 61-63 and the disks 41-43 the same as in the chuck firstdescribed. The disks 41-43 which constitute the three electrodes areconnected to the different phases of the alternating potential and thusare variably polarized following the wave forms of FIG. 13. As a result,the shear resistance of the disk-like films of liquid spaced along theshaft is increased thus exerting a viscous drag and retarding torque onthe disks 60-62 to arrest the motion of the shaft when the capacitorsare excited by closure of the control switch S.

Through the use of the present invention, it is possible to form acontrol valve having no moving parts but operable to regulate andinterrupt the flow of liquid in a fluid transfer system. Such anadaptation is shown in FIGS. 9-12 in which liquid is placed underpressure by a motor driven pump 71 and the flow thereof to and from apiston and cylinder type servo 72 is controlled by a valve 73 interposedin the pressure line 74 leading to the servo. The fiuid 70 filling thesystem may be any one of the electro-viscous mixtures described above.

As shown in FIG. 10, the valve 73 includes a tubular casing 75 composedof insulating material having an internal cylindrical surface 76concentric with and surrounding the cylindrical external surface of arod 78, the two surfaces defining between them a tubular space, usuallyabout .010 in radial thickness, through which the liquid may flow freelywhen not activated.

Herein, the rod 78, which is composed of conductive material or anon-conductive material coated with electrically conductive material ormaterial of high dielectric constant, is seated at opposite ends indisks 79 supported by hollow fittings 74a threaded onto opposite ends ofthe valve casing 75 and the adjacent portions of the liquid conduit 74.Apertures 89 in the disks allow for the free flow of the liquid throughthe valve casing when and formed around the interior of the casing 75.Within and in close contact with the electrode rings .are cylindricalrings 85 composed of the fired ceramic material above described having ahigh dielectric constant. These rings are. about .100 of an inch inradial thickness and their-inner surfaces are substantially flush withthe interior of the casing.

One or more groups of the electrodes 81-83 may be employed and thecorresponding and consecutively spaced electrodes of each group haveterminals extended to the exterior of the casing and connectedrespectively to the leads 21-23 of .the three phase power source. Itwill thus be apparent thatthe high dielectric rings 85 and the tube ofthe electro-viscous liquid enclosed thereby form composite electriccondensers in which an electric field and the desired displacementcurrents in the liquid will beproduced when the three phase potential isapplied to the electrodes. As a consequence and as in the chuck andbrake above described, the liquid is stiffened and virtuallysolidifiedthus interrupting the flow to theservo 72. By adjusting theslider 32 and therefore the applied potential, the flow may be regulatedand thespeed of the servo piston controlled as desired.

It will be apparent that in each of the devices described above, a layerof the electro-viscous fluid lies in contact with a layer of materialhaving a high dielectric constant and cooperating with the liquid toform an electric capacitor across which an alternating voltage ofsubstantial magnitude may be imposed to produce the desired displacementcurrents and stiffening of the liquid layer without the actualconductive fiow of current that might other- .wise break-down orcarbonize the liquid. Because of this, anelectric field of substantiallygreater intensity for a given thickness of the electro-viscous film canbe produoed and thicker or thinner films may be employed as is desirablefor certain applications. Also, the separation of the electro-viscousfilm from the electrodes by the dielectric insulating layer 19eliminates any danger of short-circuiting the electrodes as byconductive coolant that may-flow onto the work. For the same reason, theholding power of the film is not reduced by dirt or other contaminantsthat may be present or enter the liquid in service use.

In different electro-responsive devices such as those illustrated, theelectrodes and the dielectric layers may take various forms depending onthe use involved and for manufacturing economies. Also, the number ofgroups of the polyphasc electrodes may be varied as desired to achievethe desired total shear or flow resistance when the electro-viscouslayer is activated.

As used in the appended claims, an electro-viscous liquid contemplatesand includes a flowable liquid which stifiens and bonds to its confiningsurfaces when an electric potential is impressed across the latter. Ahigh dielectric constant contemplates a value more than ten.

I claim as my invention:

1. An electrostatic device comprising two electrically conductivemembers having opposed closely spaced and substantially parallelsurfaces, a body of electrical insulation supporting said members andisolating the same from each other, a thin layer of solid materialhaving a high dielectric constant covering and lying against one of saidsurfaces, a film of electro-viscous liquid disposed between and inelectrical contact with said layer and the opposed one of said surfacesand cooperating therewith to form an electric condenser, and selectivelycontrollable means for impressing an alternating current voltage acrosssaid members.

2. An electrostatic device comprising means providing a polyphase sourceof electric potential having a plurality of output terminals for thediiferent phases, a plurality of metallic electrodes respectivelyconnected to said output terminals and providing surfaces laterallyspaced apart but substantially flush with each other, means supportingsaid electrodes in electrically isolated relation, layers of materialhaving a high dielectric constant covering and lying in contact withsaid electrode surfaces, electro-viscous liquid covering all of saidlayers and cooperating therewith to form composite electric condensers,and a layer of solid material confining said liquid and providing abridge across said electrodes for the electric field created in theliquid when subjected to said potential.

3. The combination in an electrostatic device of, a solid base composedof electrical insulation, strips of metal mounted in said base below thesurface thereof and disposed substantially flush with each other whilebeing spaced apart laterally, layers of material of high dielectricconstant rigid with said base and covering and lying in electricalcontact with the outer surfaces of said strips, the opposite surfaces ofsaid layers being flush with'each other and forming a rigid exposedsurface, a film of electro-viscous liquid covering said exposed surface,a rigid member lying in contact with the opposite surface of said filmand bridging said layers, said strips, said layers, said film and saidmember constituting two electrical condensers connected in seriesrelation by the member, means providing a source of alternating electricpotential, and means connecting said source and said strips tooppositely polarize the latter.

4. An electrostatic device as defined in claim 3 in which the opposedsurfaces of said layers and said member are substantially flat anddisposed in closely spaced parallel planes.

5. An electrostatic device as defined in claim 3 in which the opposedsurfaces of said body and said memher are annular and confine said filmin the form of a tube.

6. The combination in an electrostatic device of, spaced metallicelectrodes, layers of material of high dielectric constant rigidcovering and lying in electrical contact with said electrodes, theopposite surfaces of said layers being exposed, a film ofelectro-viscous liquid covering said exposed surfaces, a rigid memberlying in contact with the opposite surface of said film and bridgingsaid layers, said electrodes, said layers, said film and said memberconstituting two electrical condensers connected in series relation bythe member, means providing a source of alternating electric potential,and means connecting said source and said strips to oppositely polarizethe latter.

7. An electrostatic device as defined in claim 6 in which saidelectrodes and said member are mounted for relative rotation about apredetermined axis.

8. An electrostatic device as defined in claim 7 in which saidelectrodes, said layers, and said member comprise rings spaced alongsaid axis.

9. An electrostatic device comprising two electrically conductivemembers having opposed closely spaced and substantially parallelsurfaces, a body of electrical insulation supporting said members andisolating the same from each other, a pair of thin layers of solidmaterial having a high dielectric constant covering and lying againsteach of said parallel surfaces, respectively, a film of electro-viscousliquid disposed between and in electrical contact with said layers andcooperating therewith to form an electric condenser, and selectivelycontrollable means for impressing an alternating current voltage acrosssaid members.

10. An electrostatic device comprising at least two electrodespositioned in spaced apart relationship to define therebetween a path offlow of electricity, a layer of material having a relatively highdielectric constant and a film of electro-viscous fluid having arelatively low dielectric constant interposed in the said path of flowof electricity, said layer being sized and positioned to limit said pathof flow of electricity, said layer, film and electrodes being inelectrical contact with each other to thereby form an electriccondenser, and means for applying an alternating electric potentialacross said electrodes.

11. An electrostatic device comprising a pair of opposed electrodesspaced apart to define therebetween a path of flow of electricity, alayer of material having a relatively high dielectric constantinterposed in the said path of flow of electricity and being sized andpositioned to overlay and completely cover one of said electrodes, atfilm of electro-viscous fluid having a relatively low dielectricconstant interposed between said layer and the other one of saidelectrodes, said layer, film and electrodes being in electrical contactwith each other to thereby form an electric condenser, and means forapplying an alternating electric potential across said electrodes.

12. In an electrostatic device comprising at least two electrodespositioned in spaced apart relationship to define therebetween a path offlow of electricity, a film of electro-viscous fluid having a relativelylow dielectric constant interposed in the said path of flow ofelectricity, and means for applying an alternating electric potentialacross the electrodes to thereby form an electric condenser, theimprovement which comprises means for increasing the intensity of theelectrical field in the electroviscous fluid film and thereby increasingthe shear resistance of the film comprising a layer of material having arelatively high dielectric constant interposed between the electrodesand being sized and positioned to limit said path of flow ofelectricity.

13, An electrostatic device comprising means providing a source ofelectric potential having a plurality of output terminals, a pluralityof metallic electrodes respectively connected to said output terminalsand providing surfaces laterally spaced apart but substantially flushwith each other, means supporting said electrodes in electricallyisolated relation, layers of material having a high dielectric constantcovering and lying in contact with said electrode surfaces,electro-viscous liquid covering all of said layers and cooperatingtherewith to form composite electric condensers, and a layer of solidmaterial confining said liquid and providing a bridge across saidelectrodes for the electric field created in the liquid when subjectedto said potential.

14. An electrostatic device as defined in claim 1 in which said layerand the opposed one of said surfaces cooperate to define an annularpassage of narrow radial width, and further including means for forcinga flow of said fluid longitudinally through said passage to form saidfilm therein whereby said device constitutes a valve for controllingsaid flow in accordance with said voltage.

References Cited in the file of this patent UNITED STATES PATENTS2,417,850 Winslow Mar. 25, 1947 2,859,962 Beveridge Nov. 11, 19582,897,424 Waring July 28, 1959 2,897,425 Waring July 28, 1959 2,904,431MoncrieiT-Yeates Sept. 15, 1959 2,923,390 Fitch Feb. 2, 1960

1. AN ELECTROSTATIC DEVICE COMPRISING TWO ELECTRICALLY CONDUCTIVEMEMBERS HAVING OPPOSED CLOSELY SPACED AND SUBSTANTIALLY PARALLELSURFACES, A BODY OF ELECTRICAL INSULATION SUPPORTING SAID MEMBERS ANDISOLATING THE SAME FROM EACH OTHER, A THIN LAYER OF SOLID MATERIALHAVING A HIGH DIELECTRIC CONSTANT COVERING AND LYING AGAINST ONE OF SAIDSURFACES, A FILM OF ELECTRO-VISCOUS LIQUID DISPOSED BETWEEN AND INELECTRICAL CONTACT WITH SAID LAYER AND THE OPPOSED ONE OF SAID SURFACESAND COOPERATING THEREWITH TO FORM AN ELECTRIC CONDENSER, AND SELECTIVELYCONTROLLABLE MEANS FOR IMPRESSING AN ALTERNATING CURRENT VOLTAGE ACROSSSAID MEMBERS.